Froth flotation machine with liquid level control weir



W. H. KELSEY FROTH FLOTATION MACHINE WITH LIQUID LEVEL CONTROL WEIR 2 Sheets-Sheet 1 Filed Nov. 25, 1950 FIG.

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Oct. 2, 1956 W. H. KELSEY FROTH FLOTATION MACHINE WITH LIQUID LEVEL CONTROL WEIR Filed Nov. 25, 1950 2 S eets-Sheet 2 l3 57 35 14- 38 38 2O 55 \s \6 24- 34 2s 38 1 51 5O '52 35 27 I9 22 z, 42 Z 52 57 Q 4 22 5 3s 33 44 i aa-l 2o s4 53 INVENTOR:

l} HAM HKELSEY, aulL ATTORNEYS.

United States Patenp 2,765,073 Fatented Oct. 2, i956 FROTH FLOTATION MACHINE WITH LIQUID LEVEL CONTROL WEIR William H. Kelsey, Bauer, Utah, assignor to Combined Metals Reduction Company, Salt Lake City, Utah, a corporation of Utah Application November 25, 1950, Serial No. 197,557 12 Claims. (Cl. 209-169) This invention relates to flotation machines as commonly employed in froth flotation practice, for example in the aeration of metallurgical pulps for the recovery of metallic values.

A principal object of the invention is to provide a flotation machine having substantially no dead zones for either the stagnation of pulp being aerated, or of the froth so formed, so that vigorous and eflicient aeration of pulp will be obtained throughout substantially the entire volumetric extent of the agitation chambers of individual flotation cells and so that eflicient recovery of froth will be had.

This is accomplished primarily by the provision of a novel transition or junction box between cells of the machine, for the discharge of tailings from one cell and for the introduction of these tailings as feed pulp to the cell next succeeding, essentially similar boxes being provided at the head and at the tail end of the machine for the initial feed of pulp to and the final discharge of tailings from the machine as a whole.

A correlated object, achieved coincidentally, is to obtain higher recoveries than have heretofore been customary in flotation practice, and to do this by the use of a machine which occupies less space than is customary.

Other objects of the invention are:

To provide a flotation cell whose pulp level is subject to precise control at all times during operation.

To improve the recirculation of pulp, and to provide for better control of pulp flow and recirculation.

To reduce wear and sanding of a flotation cell.

To simplify flotation machine construction, and to provide for more economical fabrication.

Features of the invention, additional to the abovementioned transition or junction box, include a variableheight overflow weir disposed within the transition or junction box, and a novel arrangement of pulp flow channels, i e-circulation ports, and adjustable re-circulation baflles, as well as various structural details.

Further objects and features of the invention will be apparent from the following detailed description of a presently preferred form thereof illustrated in the accompanying drawings to exemplify the generic structural concepts involved.

In the drawings:

Fig. 1 represents a top plan view of a flotation machine made up of two flotation cells, the overflow weir of the first cell providing for discharge into the second cell at the proper pulp level, and the overflow weir of the second cell maintaining the proper pulp level therein while providing a tailings discharge;

Fig. 2, a longitudinal vertical section taken on the line 2-2 of Fig. 1, illustrating one of the overflow weirs largely in elevation;

Fig. 3, a transverse vertical section taken on the line 3-3 of Fig. 1;

Fig. 4, a similar section taken on the line 4-4 of H s Fig. 5, a horizontal section taken on the line 5--5 of Fig. 2; and

Fig. 6, a fragmentary horizontal section taken on the line 6-6 of Fig. 2.

Referring to the drawings: in the particular form illustrated, the flotation machine comprises two flotation cells 10 and 11 arranged in series, as is customary, so that pulp is fed at one end and tailings discharged at the other. Any desired number of cells may, of course, be included in a single machine, the transition structure from cell to cell being identical in all instances.

Each cell constitutes a walled container for pulp, the container being fabricated from any suitable material, preferably steel plates welded together. Oppositely disposed side walls 13, Fig. 3, slope upwardly and outwardly from a centrally disposed bottom wall 14, and terminate in respective longitudinally extending froth overflow lips 15 laterally of the machine. At the front of the machine, an end wall 16, Fig. 1, closes the first cell 10 and partially defines a pulp feed box 17, while, at the rear, an end wall 18 serves, in conjunction with a tailings outflow box 19, to close the second cell 11. An intermediate partition wall 20 serves, in conjunction with a transition box 21, to divide the two cells from each other.

Upon the bottom wall 14 of each cell a pulp flow conduit 22 is defined by means of oppositely disposed side walls 23, which are conveniently structural steel channels, as shown, and by a top wall 24. The forward end of each conduit 22 is open for the inflow of pulp, but the opposite end is largely closed by a wall 25, conveniently provided, in this instance also, by a structural steel chan- 'nel.

Superimposed upon the top wall 24 of each pulp flow conduit 22, and communicating with such conduit through a suitable opening 26, is a pulp aeration and agitation assembly, here shown as a rotor-stator unit 27 of the well known Fagergren design. An electric motor 28, mounted on a bracket standard 29 which rises from securement, at its base, to a pair of transversely spaced, longitudinally extending beams 30, preferably structural steel angles, as shown, serves to drive the shaft 31 of rotor-stator unit 27 by means of the usual belt drive arrangement 32. An air tube 33 conducts atmospheric air from above the froth level of the cell to the rotor, in customary fghion.

Diverging outwardly from origins along the longitudinal central axis of the machine, at the front and the back of respective rotor-stator units 27, and extending transversely of the respective cells, are pulp-deflecting baffles 34, which, in the case of the pulp transition box 21, provide the four side walls therefor, and, in the case of both the pulp feed box 17 and the tailings outflow box 19, provide important parts of the side walls thereof. It will be noted that such pulp-deflecting baflles 34 serve to crowd aerated pulp and the superimposed froth outwardly toward the side walls 13 of the cell, and also wall-in what would otherwise be dead areas within the cell.

It is within certain of these otherwise dead areas that overflow weir structure is placed to singular advantage. It is preferred that such overflow weir structure be of the novel construction here disclosed and claimed.

Thus, in both the pulp transition box 23, between the two cells 10 and ii, and in the tailings outflow box N there are provided respective centrally disposed upstanding pipes 35 having diameters slightly less than the diameters of the tubular bellows 36 of the overflow weirs and serving as lower anchorages and pulp inlets theretor.

As illustrated, the respective boxes are provided with floors 37 at the level of the top wall of the pulp flow conduits 22 and comprehending the forward halves of such boxes, making tight joinders with portions of the partition Wall 20 and the end wall 18, respectively, which protrude into the respective bOXes at and below the floor level, as well as with the forwardly disposed semi-circumferences of the pipes 35. Below such floors 37, and between the closed ends of the pulp floor conduits 22 and the partition wall 20, on the one hand, and the end wall 18 on the other, respective pulp flow channels 38 lead from respective bubble chambers 39 of the cells and 11, through openings 38-1 cut through extensions of the structural steel channels 23, to preferably semicircular openings 40 formed through forward and lower portions of the respective pipes 35, thereby providing flow passage for tailings from the respective cells into 1 the respective overflow weirs.

The upper ends of the pipes 35 project upwardly from floor level, and have closely fitted thereon the lower open ends of the respective tubular bellows 36. Respective clamping collars 41 effect tight sealing of the joinders.

The open upper ends of the tubular bellows 36 are fitted about the rims of respective spiders 42, fixed to the lower ends of respective threaded shafts 43. Respective clamping collars 44 effect tight sealing of the joinders.

The screw shafts 43 pass through respective crossbars 45, which extend transversely of the respective cells 10 and 11 and are secured to the longitudinally extending beams 30. Miter gears 46 are threaded on the respective screw shafts 43, and, by means of respective meshing miter gears 47 fixed to respective actuating cranks 48, serve to raise or lower the respective screw shafts 43 and their spiders 42. Manual turning of the crank handles 48a, then, effects either raising or lowering of the respective weir crests 49 to the extent desired.

It should be noted that the overflow weir structure is disposed, in each instance, wholly within the particular tailings outflow box concerned, whether such box be a transition or junction box between successive cells within a single machine, or a tailings outlet box leading from the last cell in a series and serving the machine as a whole. With the flotation cell constructed as it is, such a tailings outflow box occupies what would otherwise be dead space so far as froth recovery from the cell is concerned.

In the illustrated instance, pulp to be processed enters the machine through a pipe 50 leading upwardly into pulp feed box 17 through the bottom thereof. However, if desired, the pulp may be introduced to feed box 17 through its open upper end or through the end wall 16 in any suitable manner.

Tailings leave the machine through a pipe 51 leading from tailings outflow box 19 through the bottom thereof. Froth discharging over the lips passes into conventional launders (not shown) for recovery.

Recirculation ports 52 for pulp are provided at closely spaced intervals along the lengths of the side walls 23 and end walls 25 of the respective pulp flow conduits 22, and adjustably positioned bafiles 53 advantageously extend longitudinally of the respective bubble chambers 39 to direct pulp recirculation. The bottom edges of such baffles 53 pivotally engage the upper longitudinal edges of the respective pulp flow conduits 22, as by means of longitudinal, half-round, concave strips 54 secured, as by welding, to such upper longitudinal conduit edges, and are adjustably suspended from the upper parts of the end walls of the machine, as by means of hangers 55 engaging selected teeth of respective racks 56. They are preferably made up of individual longitudinal strips slidably positioned within channel slideways 53-1 at opposite ends of the respective bafflcs, so strip may be either added or removed to alter the battle height when desired.

Bleeder ports 57 are advantageously provided through the respective pipes 35 of the two cells 10 and 11.

In operation, pulp to be processed flows into pulp feed box 17 through the feed pipe 50, and passes into the pulp flow conduit 22 of cell 10 through the open bottom of pulp feed box 17. The pulp is drawn into the rotor of the rotor-stator unit 27 through the opening 26 in the top of conduit 22, and is flung outwardly in aerated condition through the stator of such unit into the respective bubble chambers 39 of the cell, where it is directed upwardly in the form of respective sorting columns by recirculation baffles 53 to provide for easy escape of bubbles to the surface and effective froth pulp discharge over the froth overflow lips 15. The depleted pulp passes back under the baflles 53 and through the laterally disposed recirculation ports 52 into the pulp flow conduit 22 for re-passage through the rotor-stator unit 27. Tailings from this first cell 10 pass out of the bubble chambers 39 and into the lower end of the overflow weir structure through respective openings 381, respective pulp flow channels 38, and opening 40, in pipe 35, and pass upwardly through the hollow interior of the tubular bellows 36 and over the Weir crest 49 into the transition or junction box 21.

It should be noted that the level of the weir crest 49 determines the level of pulp within the cell, and that such level is adjusted from time to time in accordance with various operating requirements, as is customary in the flotation art. Such weir crest level can be precisely adjusted by merely turning the crank handle 48a to the desired extent, in one direction or the other.

The tailings from the first cell 10, flowing over the weir crest 49 of the overflow weir structure, at any given adjustment thereof, in quantity determined by the feed of pulp to the cell, pass into the transition or junction box 21 and through the open rearward portion 58, Fig. 2, of the bottom thereof into the pulp flow conduit 22 of the second cell 12, thereby providing pulp feed for such second cell. Such pulp passes through the second cell 12 in the same manner as described for the first cell, the tailings therefrom similarly passing into and through the hollow interior of the tubular bellows 36 of the overflow weir structure within tailings outflow box 19, and over the weir crest 49 thereof, into such tailings outflow box 19, from which they discharge from the machine through the outflow or discharge pipe 51. The weir crest 49 of this second weir structure is positioned and controlled in the same manner as that of the first. Accordingly, the pulp level of levels in the machine are under precise control at all times.

It can be easily seen that the walls 34 of the diamondshaped transition or junction box 21, in conjunction with the similar walls 34 of the triangular pulp feed box 17 and forward portion of tailings outflow box 19, serve to crowd aerated pulp emanating from the rotor-stator units 27 toward the lateral sides of the respective cells, thereby eliminating what would otherwise tend to be dead or static zones in the areas occupied by the respective boxes.

Since such walls preferably extend throughout the complete height of the cells, they also serve to crowd the superimposed froth toward the discharge lips 15 at opposite lateral sides of the respective cells.

It should be noted that the underlying pulp acts partially as a froth-conveying medium to the boundaries established by the outward terminations of the recirculation baflles 53, where separation of froth from pulp is facilitated. By virtue of their adjustability with respect to slope and height, the recirculation bafiles can be made to cut the bubble column at any desired level.

The pulp flow conduit 22 and recirculation ports 52 make for positive pulp flow within the individual cells, thereby reducing sanding and wear, while the overflow weirs and recirculation baffles afford precise control of pulp levels and pulp recirculation throughout the machine. Short circuiting of pulp is prevented, and positive recirculation back through the rotor is assured.

' The flat,vnon-cascading design of the machine simplifies construction, and enables economical fabrication from steel plates and rolled structural shapes extending integrally from cell to cell.

Whereas this invention is here illustrated and described with respect to a particular preferred embodiment thereof, it should be understood that various changes, apart from the mere substitutions of equivalents, may be made therein and various other constructions may be adopted on the basis of the teachings hereof, by those skilled in the art, without departing from the protective scope of those of the following claims which are generic to the broader inventive concepts disclosed.

I claim:

1. In a flotation machine, a flotation cell comprising walls defining an open chamber for pulp; a pulp feed box at one end of said chamber; a tailings outflow box at the opposite end of the chamber; a pulp flow conduit at the bottom of the chamber and leading from said pulp feed box to said tailings outflow box; a pulp-frothing impeller mounted for rotation on a substantially vertically disposed axis, above and in flow communication with said conduit and intermediate the said pulp feed box and the said tailings outflow box, so as to draw pulp from said conduit and discharge aerated pulp outwardly into the chamber; pulp and froth deflecting walls rising substantially vertically from the bottom of the chamber at opposite ends thereof and in respective substantially V form'ations to partially define said pulp feed and said tailings outflow boxes, said deflecting walls diverging outwardly toward opposite sides and the respective ends of the chamber from vertices lying in a substantially common plane with the said axis of the impeller; and means establishing pulp flow communication between the chamber and the tailings outflow box.

2. The combination recited in claim 1, wherein the pulp flow communication means comprises a tubular overflow Weir for tailings disposed within the tailings outflow box in flow-receiving communication with the said chamber, and an outlet for tailings is provided at a low level in the said tailings out-flow box.

3. The combination recited in claim 2, wherein pulprecirculation ports establish flow communication between the chamber and the pulp flow conduit.

4. The combination recited in claim 3, wherein bleeder ports establish flow communication between the overflow weir and the pulp flow conduit.

5. A flotation machine, comprising a series of flotation cells as recited in claim 1, the tailings out-flow box of any one cell being merged with the pulp feed box of the cell next succeeding to form a single, dual-purpose box of substantially diamond shape.

6. The combination recited in claim 5, wherein all the cells of the series are located on a common level.

7. The combination recited in claim 1, wherein the pulp flow conduit is narrower than the floor of the said chamber, and is superimposed upon said floor intermediate the width thereof; and wherein a multitude of pulp-recirculation ports are provided through opposite side walls of said conduit and along the lengths thereof.

8. A flotation cell, comprising walls defining an open chamber having oppositely and laterally disposed froth overflow lips; frothing means disposed substantially centrally of said chamber; and sets of divergent pulp and froth deflecting baifles disposed at respectively opposite ends of the chamber, the battles of each of said sets of baffles rising substantially vertically from bottom to top of said chamber and diverging away from said frothing means and toward said overflow lips from a closed mutual joinder, to define therebetween a space closed off from said frothing means.

9. The combination recited in claim 8, wherein pulp feed means is disposed at least partially in said space defined by the baffles of one of said sets, and tailings outflow means is disposed at least partially in said space defined by the baflles of the other of said sets.

10. In a flotation machine having at least two cells aligned end to end so that tailings flow from the first into the second, walls defining a combination tailings out-flow and pulp feed box between the two cells; a tubular flexible bellows disposed within said box as an overflow weir; conduit means leading from the first cell into the lower part of said bellows; means for raising and lowering the upper part of said bellows to vary the weir level; and conduit means leading from said box into the second cell.

11. In a flotation machine, a flotation cell comprising walls defining an open chamber for pulp; a pulp feed box at one end of said chamber; a tailings outflow box at the opposite end of the chamber; a pulp flow conduit at the bottom of the chamber and leading from said pulp feed box to said tailings outflow box; a pulp-frothing impeller mounted for rotation on a substantially vertically disposed axis, above and inflow communication with said conduit and intermediate the said pulp feed box and the said tailings outflow box, so as to draw pulp from said conduit and discharge aerated pulp outwardly into the chamber; pulp and froth deflecting walls rising substantially vertically from the bottom of the chamber at opposite ends thereof to partially define said pulp feed and said tailings outflow boxes, said deflecting walls diverging outwardly toward opposite sides and the respective ends of the chamber from respective longitudinal center lines lying in substantially a common plane with the said axis of the impeller; and means establishing pulp flow communication between the chamber and the tailings outflow box.

12. In flotation apparatus provided with a container for pulp, means for continuously supplying pulp to said container, means for continuously removing froth from the upper part of said container, means defining a normally submerged and open tailings discharge outlet leading from said container, and means for aerating pulp within said container, the combination with said tailings discharge outlet means of a tailings overflow weir comprising an open-ended length of flexible bellows tubing comprehending said tailings discharge outlet in fluidtight and flow communicating relationship exteriorly of said container, said bellows tubing extending upwardly to provide a tailings overflow column, the height of whose upper open end determines the operating level of pulp within said container; means holding said upper open end of the bellows tubing in open condition; and means for adjusting the height of said upper open end of the bellows tubing upwardly and downwardly.

References Cited in the file of this patent UNITED STATES PATENTS 1,277,750 Pearce Sept. 3, 1918 1,413,723 Groch Apr. 25, 1922 1,556,083 Daman Oct. 6, 1925 1,888,551 Eggert Nov. 22, 1932 1,984,366 Fahrenwald Dec. 18, 1934 2,028,179 Akins Jan. 21, 1936 2,054,249 Fagergren Sept. 15, 1936 2,143,669 Weinig Jan. 10, 1939 2,182,442 Booth Dec. 5, 1939 2,252,576 MacIntosh Aug. 12, 1941 2,413,015 Wigton Dec. 24, 1946 FOREIGN PATENTS 253,618 Great Britain June 21, 1926 405,606 Great Britain Feb. 1, 1934 

